Microsoft's Windows XP Service Pack 2 is now in the hands of more than 100 million users, the company disclosed on Wednesday. The majority of those customers, however, are consumers. Microsoft officials admit that business customers are absorbing the operating-system upgrade at a slower pace.

In the two months since its release, 106 million copies of SP2 have been distributed by Microsoft to customers around the world. The bulk of those, 90 million, were downloaded via Microsoft's Windows Update, Automatic Update, or Download Center. Another 16 million shipped on CDs.

In a statement, Microsoft said it was "pleased" with the uptake of the security-oriented SP2. But it prodded Windows XP users who haven't upgraded yet to install SP2 "as soon as possible."

Microsoft's business customers are moving slower than consumers because their upgrades can involve thousands of PCs and extensive testing for application compatibility. It can take from six months to a year for a company with 1,000 or more Windows XP machines to upgrade them all, according to Barry Goffe, a Windows group product manager.

Goffe acknowledges there's "a lot of angst" among system administrators concerning application compatibility but says many customers are getting through the testing process without running into major issues. Microsoft is developing a version of its Application Compatibility Toolkit that can be used by system administrators to automate some of the manual work involved in SP2 testing. A beta version of the tools could be ready within a few weeks.